1. Field of the Invention
The present invention relates to a motion sensing apparatus, and more particularly, to an adjustable motion sensing apparatus for decorative light fixtures.
2. Description of the Related Art
Motion sensing devices have been used in lighting control systems and security alarms for a number of years. For example, motion sensing devices for non-decorative fights usually consist of a sensing head or housing that is mounted independently of the lighting fixture. These independent housings often using a ball and socket type joint allowing the sensing apparatus to be aimed in a specific manner to optimize and customize the coverage area over which motion detection occurs.
A problem has arisen with regard to decorative lighting products which are purchased for their aesthetic appeal. The goal of merging a motion sensing device with a decorative lighting product is difficult because there is a need to conceal the sensing device or, at least, to camouflage the device so that the aesthetic appearance of the decorative lighting fixture is not disturbed or the disturbance is minimized. Because of these restraints, the motion sensing device tended to be in a fixed location.
More recently, decorative lights with motion sensing devices have been marketed where the device is rotatable around a vertical axis. In this regard, see U.S. Pat. No. 5,590,953. The rotatable motion sensing device disclosed in this patent is applied to decorative brass products. However, on decorative die cast products, the location for a sensing apparatus is more limited and again has traditionally been of a fixed or stationary design.
Fixed motion sensing devices have undesirable limitations because the coverage pattern of such devices is also fixed. There are some situations in which it is desirable to have the ability to alter the coverage pattern. For example, if a decorative light fixture is to be attached to a house that is located close to a busy street, there may be a problem. The usual objective of a consumer purchasing such a fixture is to detect people moving toward or around the house, but not to detect vehicles moving back and forth on the street or people walking past on the public sidewalk. With fixed motion sensing devices, sensitivity was lowered because the extent of the pattern could not be changed. This, of course, has the disadvantage of reducing sensitivity to the motion of people which the motion sensing device was installed to detect in the first instance. A diagram of this problem is shown in FIG. 1.
Another situation causing difficulty is where the decorative light fixture is attached to a house located on a raised patch of ground or where the light is located by a door at the top of a staircase. In both cases, the ground or staircase slopes rapidly away from the house so that the motion sensing device covers an area too far away from the house. Movement closer to the house is simply under the "coverage". A diagram of this problem is shown in FIG. 2.
There is no easy solution to these problems because designing a motion sensing device that is aimed downwardly will reduce the extent of coverage in those situations where the fixture is in a more normal setting. To create speciality fixtures for different situations will require a greatly increased inventory at the retail level and a corresponding increase in cost.
Recently, an effort to solve this problem appeared in U.S. Pat. No. 5,757,004 wherein an adjustable motion detector is disclosed. There, the sensing element itself is vertically adjustable using a mechanism that may prove to be relatively expensive.